Locking assembly for a lightweight gearbox

ABSTRACT

A lock nut and tang washer mechanism preloads and locks components in a rotating environment. A drive system mechanism preloads and locks the device in a rotating environment and provides a double locking safety requirement needed in most aircraft for applications operating in an enclosed environment. The mechanism holds a required torque for the duration of the drive system operating life without the need for periodic visual inspections.

BACKGROUND

Typical gearbox gear trains incorporate several rotating bearings, seals, and other sub-assemblies in the gearbox. The power from the aircraft engines introduce very destructive vibration levels which causes loosening of hardware in the gearbox assemblies. Current methods to prevent parts in the gearbox from coming loose and spreading themselves apart can be very time consuming to assemble. The gearbox gear train components require maintenance personnel to assemble, seat, and preload the components to a required torque while assembling a gearbox or during a gearbox repair. There are many embodiments of hardware that can be used to assist in these tasks. However, such embodiments often require three pieces of hardware to properly function. The hardware also tends to lose preload due to vibration, temperature, the reuse of existing retention hardware, or small radial movement during gearbox operation.

What is needed is a two-piece drive mechanism that preloads and locks components installed in a rotating environment and provides the double locking safety requirement needed in most aircraft for applications operating in an enclosed environment. The mechanism should also hold the required torque for the duration of the drive system operating life without the need for periodic visual inspections.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary, and the foregoing Background, is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter.

The present disclosure provides a double locking nut assembly for a lightweight gearbox. In various embodiments, the assembly includes a double row duplex ball bearing coupled with a double geared shaft inside the lightweight gearbox. A washer coupled with the nut assembly includes a plurality of tangs that are operatively disposed within grooves disposed longitudinally in threads of an adjacent gear to prevent rotation of the washer. A lock nut shoulder containing a serrated deformation locking design that allows ramps of the serration to slide up on the washer while applying installation nut torque. Embodiments of the double locking nut assembly further includes a plurality of opposing tangs that serve as a safety device within the locking nut assembly.

These and other aspects of the present system and method will be apparent after consideration of the Detailed Description and Figures herein. It is to be understood, however, that the scope of the invention shall be determined by the claims as issued and not by whether given subject matter addresses any or all issues noted in the Background or includes any features or aspects recited in this Summary.

DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

FIG. 1 depicts a partially exploded view of an embodiment of a locking assembly for a lightweight gearbox according to the present technology, wherein a locking nut is shown as attaching a double row duplex ball bearing to a double geared shaft inside a lightweight gearbox for air cushion vehicles.

FIG. 2 depicts a partial, cut-away view of one embodiment of a mechanism that seats and preloads a rotating bearing or bearing set on a shaft bearing journal within a locking assembly of the present technology.

FIG. 3 depicts an isometric view of one embodiment of a ramp spiral serration nut flange that may be used within a locking assembly of the present technology.

FIG. 4 depicts an isometric view of one embodiment of a pair of anti-rotation tangs that may be used within a locking assembly of the present technology.

FIG. 5 depicts a partial, cut-away view of one embodiment of anti-rotation slots that may be forms in threads of washer tangs of a locking assembly of the present technology.

FIG. 6 depicts an isometric view of one embodiment of a 10/20 tool spline for tightening torque within a locking assembly of the present technology.

DETAILED DESCRIPTION

Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense.

The present technology relates to lock nut and tang washer mechanisms that preload and lock components in a rotating environment. In particular, a unique drive system mechanism is presented that preloads and locks the device in a rotating environment and provides a double locking safety requirement needed in most aircraft for applications operating in an enclosed environment. This mechanism holds the required torque for the duration of the drive system operating life without the need for periodic visual inspections. One of various contemplated uses for this mechanism, shown in FIG. 2, would be to seat and preload a rotating bearing or bearing set on a shaft bearing journal and visually show an inspector that the mechanism will not come off the rotating shaft, even if the mechanism was not properly preloaded. The present technology eliminates previously known requirements for locking wires, retaining rings, and locking screws, while not affecting the assembly balance.

With reference to FIG. 1, an overview of one embodiment of a double locking nut 10 inside a lightweight gearbox 12 is depicted. The depicted locking nut 10 is shown attaching a double row duplex ball bearing 14 to a double geared shaft 16 inside a lightweight gearbox 12 for air cushion vehicles. However, other applications of the present technology are contemplated.

In various embodiments, the bearing nut properly seats the inner bearing raceways 18 and provides enough stretch in the gear shaft 16 to keep an appropriate gear-bearing assembly preload, while allowing for small changes in surface topography between the clamp-up of all shoulder surfaces. In one aspect of the present technology, the nut-washer shoulder surfaces consist of two sides of the washer 20 and one side of the nut flange 22. The lock nut shoulder 24 opposite the 30-degree tool spline 26 contains a serrated deformation locking design such that a right handed threaded nut would contain a right handed spiral ramp. This allows the ramps of the serration to slide up on the washer while applying the proper installation nut torque required to seat and preload the bearing. One such embodiment is depicted in FIGS. 1 and 3. In particular embodiments, the washer material is softer than the nut material so after the bearing run-on and installation torque is applied and recorded, the washer surface will deform and now be compliant to the serration form and offer mechanical resistance to un-torqueing the bearing nut.

In various embodiments, the washer 20 mated with the nut is not allowed to rotate. To prevent this, the washer 20 may include four or more tangs 28. The tangs 28 of the washer 20 lie in four grooves 30 disposed longitudinally in the threads of the gear. The washer's tangs 28 are highlighted in FIG. 4 and a groove 30 on the threads of the gear 32 is shown in FIG. 5. The grooves and tangs prevent washer rotational movement. Two opposing tangs 28 are bent up after the nut torque is witnessed and recorded. Each of the two of four tangs 28 that are bent up serve as the two safety devices. In particular embodiments, just one of the two bent up tangs 28 will prevent the nut from rotating off the shaft 16. The primary one-way locking feature is the deformed washer. Larger bearing nuts may require more than four tangs 28. In particular embodiments, the tool spline utilized on the bearing nut is a 30-degree, 10/20 pitch, Class 3 Spline per ANSI B91.1-1996, such as depicted in FIG. 6. It will be appreciated that the number of teeth is dependent on the size of the required nut. The torque tool required to apply the nut torque is the mate to the spline noted above. The thickness of the bearing nut is what is required to achieve at least 5 full threads of engagement. The recommended thread pitch is 16 threads per inch. This assures the serrated nut backs off the washer during the nut removal when the serrations are going against the ramp and minimizes the tearing of the washer material. The thickness of the washer is dependent on the size of the bearings or component requiring the locking feature. The washer is a onetime use in most embodiments. The nut, however, can be used many times. FIG. 1 depicts one embodiment of the usage of the locking assembly.

Although the technology been described in language that is specific to certain structures, materials, and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures, materials, and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed invention. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Unless otherwise indicated, all numbers or expressions, such as those expressing dimensions, physical characteristics, etc. used in the specification (other than the claims) are understood as modified in all instances by the term “approximately.” At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the claims, each numerical parameter recited in the specification or claims which is modified by the term “approximately” should at least be construed in light of the number of recited significant digits and by applying ordinary rounding techniques. Moreover, all ranges disclosed herein are to be understood to encompass and provide support for claims that recite any and all subranges or any and all individual values subsumed therein. For example, a stated range of 1 to 10 should be considered to include and provide support for claims that recite any and all subranges or individual values that are between and/or inclusive of the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less (e.g., 5.5 to 10, 2.34 to 3.56, and so forth) or any values from 1 to 10 (e.g., 3, 5.8, 9.9994, and so forth). 

What is claimed is:
 1. A double locking nut assembly for a lightweight gearbox, the assembly comprising: a double row duplex ball bearing operatively coupled with a double geared shaft inside the lightweight gearbox; a washer coupled with the nut assembly includes a plurality of tangs that are operatively disposed within grooves disposed longitudinally in threads of an adjacent gear to prevent rotation of the washer.
 2. The double locking nut assembly of claim 1 further comprising: nut-washer shoulder surfaces defined by two sides of a washer and one side of a nut flange, a lock nut shoulder containing a serrated deformation locking design that allows ramps of the serration to slide up on the washer while applying installation nut torque.
 3. The double locking nut assembly of claim 1 wherein: the serrations are positioned to go against a ramp direction, such that the serrated lock nut shoulder backs off the washer during nut removal and minimizes the tearing of the washer.
 4. The double locking nut assembly of claim 1 wherein: two opposing tangs are bent up after a nut torque is witnessed and recorded to serve as a safety device within the locking nut assembly. 